Loss of Dnmt1 catalytic activity reveals multiple roles for DNA methylation during pancreas development and regeneration

Department of Biochemistry and Biophysics, Programs in Developmental Biology, Genetics, and Human Genetics, Diabetes Center, and Liver Center, University of California, San Francisco, San Francisco, CA 94158-2324, USA. (
Developmental Biology (Impact Factor: 3.55). 08/2009; 334(1):213-23. DOI: 10.1016/j.ydbio.2009.07.017
Source: PubMed


Developmental mechanisms regulating gene expression and the stable acquisition of cell fate direct cytodifferentiation during organogenesis. Moreover, it is likely that such mechanisms could be exploited to repair or regenerate damaged organs. DNA methyltransferases (Dnmts) are enzymes critical for epigenetic regulation, and are used in concert with histone methylation and acetylation to regulate gene expression and maintain genomic integrity and chromosome structure. We carried out two forward genetic screens for regulators of endodermal organ development. In the first, we screened for altered morphology of developing digestive organs, while in the second we screed for the lack of terminally differentiated cell types in the pancreas and liver. From these screens, we identified two mutant alleles of zebrafish dnmt1. Both lesions are predicted to eliminate dnmt1 function; one is a missense mutation in the catalytic domain and the other is a nonsense mutation that eliminates the catalytic domain. In zebrafish dnmt1 mutants, the pancreas and liver form normally, but begin to degenerate after 84 h post fertilization (hpf). Acinar cells are nearly abolished through apoptosis by 100 hpf, though neither DNA replication, nor entry into mitosis is halted in the absence of detectable Dnmt1. However, endocrine cells and ducts are largely spared. Surprisingly, dnmt1 mutants and dnmt1 morpholino-injected larvae show increased capacity for pancreatic beta cell regeneration in an inducible model of pancreatic beta cell ablation. Thus, our data suggest that Dnmt1 is dispensable for pancreatic duct or endocrine cell formation, but not for acinar cell survival. In addition, Dnmt1 may influence the differentiation of pancreatic beta cell progenitors or the reprogramming of cells toward the pancreatic beta cell fate.

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    • "Embryos were sorted for GFP expression within 4 h of heat shock; only the brightest embryos were assessed for liver size on 5 dpf. Dnmt1 s904 mutants (Anderson et al., 2009) were obtained from M. Goll (Memorial Sloan-Kettering Cancer Center, New York, USA). Tg(fabp10:dsRed) fish (Dong et al., 2007) were obtained from D. Stainier. "
    Development 01/2015; · 6.46 Impact Factor
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    • "A more global analysis of zygotic transcription initiation in embryos in which maternal Dnmt1 has been abolished would lend support to this factor being the elusive transcriptional repressor. Early embryonic development is normal in zebrafish dnmt1 mutants, suggesting that zygotic dnmt1 has little if any role in controlling the MZT (Anderson et al., 2009; Goll et al., 2009). However, the MZT has not been studied in zebrafish embryos in which both maternal and zygotic dnmt1 function has been disrupted. "
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    ABSTRACT: The initial phases of embryonic development occur in the absence of de novo transcription and are instead controlled by maternally inherited mRNAs and proteins. During this initial period, cell cycles are synchronous and lack gap phases. Following this period of transcriptional silence, zygotic transcription begins, the maternal influence on development starts to decrease, and dramatic changes to the cell cycle take place. Here, we discuss recent work that is shedding light on the maternal to zygotic transition and the interrelated but distinct mechanisms regulating the onset of zygotic transcription and changes to the cell cycle during early embryonic development.
    Development 10/2014; 141(20):3834-3841. DOI:10.1242/dev.102368 · 6.46 Impact Factor
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    • "Interestingly, the activity of the mHDAC/Mad3 complex is dependent upon binding of serotonin during early embryogenesis. As previous studies (Yakushiji et al., 2007; Anderson et al., 2009; Stewart et al., 2009) had demonstrated that epigenetic modifications can influence regeneration, we then asked whether HDAC activity is also required for Xenopus tadpole tail regeneration. Xenopus laevis have multiple HDACs, and RNA in situ hybridization experiments showed that the Class I HDAC, HDAC1, but not the Class II HDAC, HDAC6, was expressed in regenerating tails (Tseng et al., 2011). "
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    ABSTRACT: One important component of the cell-cell communication that occurs during regenerative patterning is bioelectrical signaling. In particular, the regeneration of the tail in Xenopus laevis tadpoles both requires, and can be initiated at non-regenerative stages by, specific regulation of bioelectrical signaling (alteration in resting membrane potential and a subsequent change in sodium content of blastemal cells). Although standing gradients of transmembrane voltage and ion concentration can provide positional guidance and other morphogenetic cues, these biophysical parameters must be transduced into transcriptional responses within cells. A number of mechanisms have been described for linking slow voltage changes to gene expression, but recent data on the importance of epigenetic regulation for regeneration suggest a novel hypothesis: that sodium/butyrate transporters link ion flows to influx of small molecules needed to modify chromatin state. Here, we briefly review the data on bioelectricity in tadpole tail regeneration, present a technique for convenient alteration of transmembrane potential in vivo that does not require transgenes, show augmentation of regeneration in vivo by manipulation of voltage, and present new data in the Xenopus tail consistent with the hypothesis that the monocarboxlyate transporter SLC5A8 may link regeneration-relevant epigenetic modification with upstream changes in ion content. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.
    The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 10/2012; 295(10):1541-51. DOI:10.1002/ar.22495 · 1.54 Impact Factor
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